1. Field of the Invention
The present invention relates to a laminated semiconductor device and a fabricating method of the device including two or more stacked IC packages such as, for example, TCP's (Tape Carrier Packages) and TSOP's (Thin Small Outline Packages) mounted on at least one side of a printed wiring board and outer connection leads provided in the IC packages and stacked to be connected to terminal portions (lands) of the printed wiring board, and more particularly to fixing means of the outer connection leads to the printed wiring board.
1. Discussion of Related Art
The TCP includes a film of synthetic resin having feeding holes formed in both side thereof and leads of copper leaf or foil formed on the film and an IC chip having electrodes bonded to the leads through bumps, and includes a feature wherein the TCP can be made smaller and thinner as compared with other packages.
On the other hand, the TSOP represents an SOP having a thickness of a chip reduced from 0.4-0.5 mm to about 0.25-0.3 mm, a size of a lead frame reduced to about 0.5-0.2 mm, a height of a wire bonding structure reduced from 0.2-0.3 mm to 0.1-0.15 mm, a thickness of upper and lower plastics reduced from about 1 mm to about 0.15-0.25 mm and a thickness of an overall package reduced to about 0.8-1.2 mm, while an overall thickness of a plastic molded package is usually about 3 to 4 mm.
Techniques relating to a laminated semi-conductor device are publicly known in, for example, U.S. Pat. No. 4,996,583 disclosing a high-density mounting technique in which a plurality of TCP's are stacked. As shown in FIG. 21, the laminated semiconductor device includes four positioning pins 102 mounted on a base 106 at front, rear, right and left portions thereof, while a printed wiring board 100 is formed with holes 107 through which the positioning pins 102 are inserted.
The positioning pins 102 are inserted into the holes 107 so that the printed wiring board 100 is mounted on the base 106. Four TCP's 101 are stacked on the printed wiring board 100 and aligned vertically by means of the positioning pins 102. Then, stacked outer connection leads 103 previously plated with solder are subjected to thermo-compression bonding or heated and pressure joined by a pulse heat tool 104 from above the connection leads to bond the outer connection leads 103 to one another and lowermost leads 103 are soldered to terminal portions 105 formed on the printed wiring board 100. FIG. 22 is a partially enlarged sectional view illustrating the TCP's 101 mounted on the printed wiring board 100. In FIG. 22, numeral 108 denotes film of synthetic resins of the TCP 101 and numeral 105 denotes a semiconductor chip.
In the conventional laminated semiconductor device, as shown in FIG. 22, since the leads 103 are mounted with the tips 103a of the leads being bent upward, the fixed leads 103 tend to be separated from the tips 103a thereof and connection failure of the TCP's 101 is caused.
Further, since it is necessary to form the holes 107 in the printed wiring board 100, the printed wiring pattern is required to be designed to avoid the holes 107 and is thus redundant and complicated.
In addition, since the laminated outer connection leads are heated and pressure joined by the pulse heat tool 104 on the printed wiring board 100, the printed wiring of the printed wiring board is cut to thereby reduce the yield in manufacturing of a memory card.
Furthermore, since there are the upward bent tips 103a, an occupied area S by the TCP's 101 on the printed wiring board 100 is naturally increased to thereby impede the mounting of other electronic components and make it impossible to take sufficient space between the TCP's and the other electronic components, so that there is a possibility that the TCP's and the electronic components come into contact with each other.
In order to avoid the above problems, it is suggested that the upward bent tips 103a be cut off, although the working processes are increased so that the efficiency is deteriorated and the leads 103 are separated upon cutting of the tips so that connection failure occurs.
Further, instead of the heating and pressure joining of the connection leads by the pulse heat tool as described above, there is a reflow method in which a necessary number of TCP's which are stacked and put on the printed wiring board 100 pass through a heating furnace so that the stacked TCP's 101 are connected to the printed wiring board 100, but it is difficult to apply this method to the heating and pressure joining of the leads.
More particularly, since the leads 103 of the TCP's 101 are apt to be deformed easily because a thickness of the leads is as thin as about 35 .mu.m in recent years or the tips of the leads 103 are separated from other leads 103 by the springback upon molding of the leads 103, the bonding between the leads 103 or/and between the leads 103 and the terminals of the printed wiring board 100 is apt to be unreliable and accordingly application of the reflow method which attains good productivity is difficult.